Hydrorefining with decomposed organo-metallic catalyst



United States Patent Ofilice 3,lfil,584 Patented Dec. 15, 1964 3,161,584HYDROREFG WITH DECONLPOSED ORGANO-METALLIC CATALYST William K. T. Gleim,Island Lake, Ill., assignor to Universal Oil Products Company, DesPlaines, Ill., a conporation of Delaware No Drawing. Filed duly 2, 1962,Ser. No. 207,070 Claims. (Cl. 208-464) This invention relates to a novelprocess for hydrorefining petroleum crude oils, heavy vacuum gas oils,heavy cycle stocks, etc., and to a novel catalyst especially adaptedthereto. More specifically, the present invention involves a process forhydrorefining heavy hydrocarbon charge stocks to effect the removal ofnitrogen and sulfur therefrom, and affords unexpected advantages whenemployed for the removal of metal contaminants and/or the conversion ofpentane-insoluble asphaltenes into pentane-soluble hydrocarbon oils.

Crude petroleum oils, and also the heavier hydrocarbon fractions and/ordistillate derived therefrom, generally contain considerable quantitiesof undesirable sulfurous and nitrogenous compounds. In addition, crudeoils, and the heavy hydrocarbon fractions thereof, contain certainmetallic contaminants which have an adverse effect on the activity ofcatalysts utilized in various processes to which crude oils, or heavyhydrocarbon fractions thereof, are ultimately subjected. The most commonmetallic contaminants are nickel and vanadium, although other metalsincluding iron, copper, etc., are often present. These metals may occurin a variety of forms. They may exist as metal oxides or sulfidesintroduced into the crude oil as metallic scale or similar particles, orthey may exist in the form of water-soluble salts of such metals.Usually however, they exist in the form of stable organometalliccompounds, such as metal porphyrins and the various derivatives thereof.

Although the metallic contaminants existing in the form of an oxide orsulfide scale may be separated, at least in part, by relatively simplefiltering techniques, and the Water-soluble salts are at least in partremovable by washing and subsequent dehydration, more extensivetreatment is required to remove the stable organometallic compoundsbefore the crude oil or heavy hydrocarbon charge is suitable for furtherprocessing.

In addition to organometallic compounds, crude oils contain greaterquantities of sulfurous and nitrogenous compounds than are found inlighter hydrocarbon fractions such as gasoline, kerosene, light gas oil,etc. For example, a Wyoming sour crude, having a gravity of 232 API at60 F., contains about 2.8% by weight of sulfur and about 2700 ppm. oftotal nitrogen. Reduction in the concentration of the sulfurous andnitrogenous compounds to the extent that the crude oil or heavyhydrocarbon charge is suitable for further processing, is accomplishedwith little difficulty by conversion to hydrogen sulfide and ammoniawhich are readily removed from the system in a gaseous phase. However,reduction in the concentration of the stable organometallic compounds tothe extent that the crude oil or heavy hydrocarbon charge is suitablefor further processing, is not as readily achieved. Notwithstanding thatthe concentration of these organometallic compounds is relatively small,for example, often less than about 10 ppm. calculated as the elementalmetal, subsequent processing techniques are adversely affected thereby.For example, when a hydrocarbon charge stock containing metalliccontaminants in excess of about 3 p.p.rn. is subjected to catalyticcracking, the metals become deposited upon the catalyst, altering thecomposition thereof to the extent that undesirable by-products areformed. That is to say, the composition of the catalyst, which isclosely controlled with respect to the nature of the charge stock beingprocessed and the quality and quantity of the product desired, isconsiderably changed as a result of the metal deposition thereon duringthe course of the cracking process. As a consequence the liquid productrecovery is reduced, and coke and hydrogen are formed in excessiveamounts, the former producing relatively rapid catalyst deactivation.The presence of organometallic compounds, including metal porphyrins,has an adverse effect on other processes including catalytic reforming,isomerization, hydrodealkylation, etc.

In addition, crude oils and other heavy hydrocarbon fractions generallycontain large quantities of pentaneinsoluble materials present in theform of a colloidal suspension or dispersion difficult to contacteffectively with conventional hydrorefining catalysts. Thesepentane-insoluble materials, described as asphaltenes, are carbonaceousmaterials considered as coke precursors having a tendency to becomeimmediately deposited within the reaction zone and on the catalyticcomposite as a gummy hydrocarbonaceous residue. It is further consideredthat said asphaltenes contain the bulk of the difiicultly removablemetal contaminants as well as a considerable portion of the undesirablenitrogenous and sulfurous compounds.

The object of the present invention is to provide a process forhydrorefining heavier hydrocarbonaceous materials, particularlypetroleum crude oils, utilizing a catalyst formed in a particularmanner. In other hydrorefining processes, the metals contained withinthe crude oil charge stock are removed therefrom by deposition of thesame on the hydrorefining catalyst employed. This practice greatlyincreases the amount of catalyst in a relatively short time, precludingthe use of a fixed-bed catalyst system commonly employed in present-dayrefining operations. Slurry processes, employing catalytically activemetals deposited upon silica and/or alumina, are very erosive, and makeplant upkeep difficult and expensive. The present invention teaches theprep aration of a colloidally dispersed, unsupported catalyst useful ina slurry process, and which catalyst will not effect extensive erosionof the reaction system. The present process yields a liquid hydrocarbonproduct which is more suitable for further processing withoutexperiencing the difliculties otherwise resulting from the presence ofthe above described contaminants. The process of the present inventionis particularly advantageous in effecting the removal of organometalliccompounds without significant product loss, While simultaneouslyconverting pentane-insoluble materials into pentane-soluble liquidhydrocarbons.

In a broad embodiment, the present invention relates to a hydrorefiningcatalyst which comprises at least one decomposed xanthate complex of ametal of Groups VB, VIB, and the Iron group of the Periodic Table.

In another broad embodiment, the present invention encompasses a processof forming a hydrorefining catalyst which comprises forming ahydrocarbon solution of at least one xanthate complex of a metal ofGroups VB, VIB, and the Iron group of the Periodic Table, and heatingsaid solution at a temperature of less than about 310 C. for a timesufficient to decompose said ,xanthate complex.

The present invention involves a process for hydrorefining a hydrocarboncharge stock, which process comprises admixing said charge stock with atleast one xanthate complex of a metal of Groups VB, VIB, and the Irongroup of the Periodic Table, heating the resulting mixture at atemperature less than about 310 C. and for a time suflicient todecompose said xanthate complex, reacting the resulting colloidalsuspension with hydrogen at a temperature in excess of about 225 C. andat a pressure greater than about 500 pounds per square inch gauge, andrecovering a hydrorefined liquid product.

More specifically, the present invention affords a process forhydrorefining a petroleum crude oil containing pentane-insolubleasphaltenes which comprises admixing said crude oil with molybdenumethylxanthate, heating the resulting mixture at a temperature of lessthan about 310 C. for a time sufficient to decompose said molybdenumethylxanthate, reacting the resulting colloidal suspension with hydrogenat a temperature of from about 225 C. to about 500 C. and at a pressureof from about 500- to about 5000 pounds per square inch gauge, andrecovering said crude oil substantially free from pentaneinsolubleasphaltenes.

From the foregoing embodiments it is readily ascertained that theprocess of the present invention involves the formation of a catalystutilizing metals selected from Groups VB, VIB, and the Iron group of thePeriodic Table (Handbook of Chemistry and Physics, 43rd ed.). Thecatalyst prepared in accordance with the method of the presentinvention, may comprise one or more metals from the group consisting ofvanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron,nickel, and cobalt. The catalyst is formed by initially dissolv ing axanthate complex of the selected metal, or metals, in the hydrocarboncharge stock containing contaminating influences, includingpentane-insoluble asphaltenes which are to be converted into solublehydrocarbons. The quantity of a xanthate complex employed is such thatsaid complex comprises from about 1.0 wt. percent to about 10.0 wt.percent of the hydrocarbon charge stock, calculated as the elementalmetal. Suitable compounds which can be employed as a xanthate complexinclude niobium ethylxanthate, tantalum ethylxanthate, chromiumethylxanthate, iron ethylxanthate, nickel ethylxanthate, cobaltethylxanthate, etc., and in particular vanadium methylxanthate, vanadiumethylxanthate, vanadium propylxanthate, vanadium isopropylxanthate,vanadium butylxanthate, vanadium isobutylxanthate, vanadiumamylxanthate, vanadium isoamylxanthate, etc., and also molybdenummethylxanthate, molybdenum ethylxanthate, molybdenum propylxanthate,molybdenum isopropylxanthate, molybdenum butylxanthate, molybdenumisobutylxanthate, molybdenum amylxanthate, molybdenum isoamylxanthate,etc., and also tungsten methylxanthate, tungsten ethylxanthate, tungstenpropylxanthate, tungsten isopropylxanthate, tungsten butylxanthate,tungsten isobutylxanthate, tungsten amylxanthate, tungstenisoamylxanthate, etc. The aforementioned xanthates, as well as othersuitable xanthates, may be represented by the following generalstructural formula:

In the above structural formula, R can be a methyl, ethyl, or otheralkyl group containing up to about 20 carbon atoms, the larger alkylgroups enhancing the oil solubility characteristics of the particularxanthate complex. R may also be an alkenyl, aryl, alkaryl, or aralkylgroup. In the above formula, Me denotes a metal selected from the groupconsisting of vanadium, niobium, tantalum, chromium, molybdenum,tungsten, iron, nickel, and cobalt. In some instances, as in the case ofthe Group VB and VIB metals, Me is also representative of the metal inthe form of an oxide thereof. For example, a molybdenum xanthate may berepresented by the general formula illustrated below:

The xanthate complex of the selected metal may be prepared by anyconventional or otherwise convenient method. One suitable methodcomprises mixing an aqueous solution of the ammonium salt of theselected metal, for example ammonium molybdate, with an aqueous solutionof an alkali metal xanthate, for example, potassium ethylxanthate. Theresulting solution is neutralized with a weak acid, for example S0 toprecipitate the desired xanthate complex. The precipitate is dried, andmay be used as such or purified by recrystallization, for example, frombenzene, alcohols, paraftins, etc.

The process is effected, as hereinabove set forth, by initiallydissolving a desired quantity of the selected xanthate complex, forexample molybdenum ethylxanthate, in the hydrocarbon charge stock. Thexanthate complex may be added directly to the charge stock and dissolvedtherein. However, a preferred method comprises adding said xanthatecomplex as a solution thereof utilizing a suitable solvent such as analcohol, benzene, and the like, while maintaining the charge stock at atemperature sufficient to distill the solvent therefrom substantiallyimmediately as added. In either case the resulting mixture is thenheated at a temperature less than about 310 C. for a time sufficient toeffect decomposition of the xanthate complex, thereby forming thecatalyst as a colloidal suspension, or dispersion, within thehydrocarbon charge stock. The decomposition of the xanthate complex isconducted at a temperature less than about 310 C. in order to avoidinitial cracking of the petroleum crude oil prior to effecting completedecomposition of the xanthate complex.

The presence of free hydrogen during the above described decompositionprocedure tends to have an adverse effect on catalyst activity withrespect to the conversion of the pentane-insoluble fraction and removalof organometallic compounds. It is therefore preferred to exclude freehydrogen during said decomposition procedure. On the other hand,hydrogen sulfide appears to have a beneficial effect and its presence ispreferred during the decomposition procedure as well as the subsequenthydrorefining procedure. The colloidal suspension or dispersion thusprepared is reacted with hydrogen at a temperature is excess of about225 C., preferably at a temperature of from about 225 C. to about 500C., and at a hydrogen pressure in excess of about 500 p.s.i.g.,preferably at a pressure of from about 500 to about 5000 p.s.i.g. Thislast mentioned treatment with hydrogen results in the conversion of asubstantial portion of the pentaneinsoluble asphaltenes topentane-soluble hydrocarbons. In addition there is further formed whatis herein referred to as a catalyst sludge which is readily separatedfrom the hydrorefined product. Said catalytic sludge comprisesunconverted asphaltenes, catalyst, and pentanesoluble hydrocarbons aswell as the metal portion of the hydrocarbon charge stock separatedtherefrom. The process of this invention may be effected in any suitablemanner and may comprise either a batch or a continuous type ofoperation. For example, when a batch type of operation is employed,hydrogen and the hydrocarbon charge stock containing the colloidallydispersed catalyst are charged to an enclosed vessel and maintainedtherein at the desired temperature and pressure and with stirring. Oncompletion of the hydrorefining process, the normally liquidhydrocarbons are separated from the reaction mixture by any suitablemeans, for example, through the use of a centrifuge or by means of asettling tank, the resulting catalyst sludge being recovered for re-useas such, or converted back to the xanthate complex by any of thewell-known chemical means. The ammonia and hydrogen sulfide, resultingfrom the destructive conversion of sulfurous and nitrogenous compoundscontained within the petroleum crude 'oil, may be removed in a gaseousphase along with any light paraffinic hydrocarbons such as methane,ethane, and propane, etc. In a continuous type of operation, thestarting materials, comprising hydrogen and the colloidal suspension,are continuously charged to a reactor maintained at the properconditions of temperature and pressure. The reaction mixture iscontinuously withdrawn from the reactor at a rate which will insure anadequate residence time therein. The hydrorefined product may beseparated from the reactor efiluent in the above described manner andthe catalyst sludge recycled as a portion of the charge to the aforesaidreactor.

The following example Will serve to further illustrate the process ofthis invention and the advantages to be derived therefrom with respectto separation of contaminating metals, pentane-insoluble asphaltenes,and nitrogenous and sulfurous compounds from the crude 'oil chargestock. It is not intended that the present invention be unduly limitedto the catalyst, charge stock, and/ or operating conditions employedWithin the example.

A Wyoming sour crude oil is utilized as a charge stock to illustrate theprocess of this invention. Such a charge stock has been found to containabout 2.8 Wt. percent sulfur, approximately 2700 ppm. of nitrogen, 18ppm. of nickel and 71 ppm. of vanadium as stable metal porphyrins,computed as the elemental metal. In addition, the sour crude contains8.37 wt. percent pentaneinsoluble asphaltenes. As hereinafter indicated,the process of the present invention effects the conversion of asubstantial portion of said asphaltenes to the extent that the same nolonger exert a detrimental efiect on subsequent processing procedures.

A rotating steel autoclave of about 800 cc. capacity is utilized as areaction vessel to illustratethe process of this invention. and about 30g. of molybdenum ethylxanthate are charged to the autoclave. The mixtureis heated at about 250 C. to etfect the decomposition of the molybdenumethylxanthate, thus forming the catalyst as a colloidal suspension ordispersion in the crude oil. thereafter sealed, pressured With hydrogen,and heated at about 400 C. over about an 8 hour period. An initiallyimposed hydrogen pressure of about 100 atmosphercs at about roomtemperature is suitable, rising to about 200 atmospheres at reactiontemperature. At the expiration of the aforesaid 8 hour period, theautoclave contents are cooled and the autoclave is depressured. Thereaction mixture is centrifuged and the supernatent liquid hydrocarbonproduct recovered. The liquid hydrocarbon, hydrorefined in the aforesaidmanner, and will indicate less than about 0.5 wt. percent pentaneinsoluble asphaltenes. In addition, there will be present less thanabout 100 p.p.m. of nitrogen, 0.10 wt. percent sulfur, 0.05 p.p.m. ofnickel, 0.01 ppm. of vanadium.

The foregoing specifications and example will illustrate the advantagesaiforded the hydrorefining of petroleum crude oils due to utilization ofthe process of this invention. It is of particular interest to note thatthe nickel and vanadium porphyrin concentration, as well as thepentaneinsoluble asphaltene concentration, is decreased to a levelpermitting subsequent utilization of the crude oil for furtherprocessing.

I claim as my invention:

1. A method of producing a catalyst which comprises forming ahydrocarbon solution of at least one xanthate complex of a metalselected from the group consisting of vanadium, niobium, tantalum,chromium, molybdenum, tungsten, iron, nickel and cobalt, and heatingsaid solution at a temperature less than about 310 C. for a timesufiicient to decompose said xanthate complex.

About 200 g. of the aforesaid crude oil The autoclave is 2. A process ofclaim 1 further characterized in that said xanthate complex comprises axanthate complex of molybdenum.

3. A process for hydrorefining a hydrocarbon charge stock whichcomprises admixing said charge stock with at least one xanthate complexof a metal selected from the group consisting of vanadium, niobium,tantalum, chromium, molybdenum, tungsten, iron, nickel and cobalt,heating the resulting mixture at a temperature of less than about 310 C.and for time sufficient todecompose said xanthate complex, reacting theresulting colloidal suspension with hydrogen at a temperature in excessof about 225 C. and at a pressure greater than about 500 pounds persquare inch gauge, and recovering a hydrorefined liquid product.

4. The process of claim 3 further characterized in that the colloidalsuspension of said charge stock and decomposed xanthate complex isreacted with hydrogen at a temperature of from about 225 C. to about 500C. and under an imposed pressure of from about 500 to about 5000 poundsper square inch gauge.

5. The process of claim 3 further characterized in that said xanthatecomplex is a xanthate complex of molybdenum.

6. A process for hydrorefining a petroleum crude oil containingpentane-insoluble asphaltenes which comprises admixing said crude oilwith at least one xanthate complex of a metal selected from the groupconsisting of vanadium, niobium, tantalum, chromium, molybdenum,tungsten, iron, nickel and cobalt, heating the resulting mixture at atemperature less than about 310 C. and for a time suflicient todecompose said xanthate complex, reacting the resulting colloidalsuspension with hydrogen at a temperature in excess of about 225 C. andat a pressure greater than about 500 pounds per square inch gauge, andrecovering said crude oil substantially free of pentane-insolubleasphaltenes.

7. The process of claim *6 further characterized in that said xanthatecomplex is decomposed within said crude oil in a non-reducingatmosphere.

8. The process of claim 6 further characterized in that the mixture ofsaid crude oil and decomposed xanthate complex is reacted with hydrogenin the absence of carbon monoxide.

9. The process of claim 8 further characterized in that said xanthatecomplex is a xanthate complex of molybdenum.

10. A process for hydrorefining a petroleum crude oil containingpentane-insoluble asphaltenes which comprises admixing said crude oilwith molybdenum ethylxanthate heating the resulting mixture at atemperature of less than about 310 C. for a time suflicicnt to decomposesaid molybdenum ethylXanthate, reacting the resulting colloidalsuspension with hydrogen at a temperature of frorr about 22 C. to about500 C. and at a pressure of frorr about 500 to about 5000 pounds persquare inch gauge and recovering said crude oil substantially free ofpen tans-insoluble asphaltenes.

References Cited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF PRODUCING A CATALYST WHICH COMPRISES FORMING AHYDROCARBON SOLUTION OF AT LEAST ONE ZANTHATE COMPLEX OF A METALSELECTED FROM THE GROUP CONSISTING OF VANADIUM, NIOBIUM, TANTALUM,CHROMIUM, MOLYBDENUM, TUNGSTEN, IRON, NICKEL AND COBALT, AND HEATINGSAID SOLUTION AT A TEMPERATURE LESS THAN ABOUT 310*C. FOR A TIMESUFFICIENT TO DECOMPOSE SAID XANTHATE COMPLEX.